All 10 people who had shown symptoms of the Middle East Respiratory Syndrome (MERS) tested negative for the disease, health authorities said Wednesday.

The Korea Centers for Disease Control and Prevention (KCDC) said one person who came into close contact with a MERS patient and another nine people who came into ordinary contact, and who had been placed under quarantine have all been released as they did not have the potentially life-threatening disease.

The released people, however, will further be monitored by the KCDC, officials said.

On Saturday, a 61-year-old man was diagnosed with the disease after returning home from his visit to Kuwait. He was rushed to the emergency room of Samsung Medical Center in southern Seoul upon his arrival at Incheon International Airport.

As of 6:00 p.m. Tuesday, a total of 21 people who had come in close contact with the MERS patient, including those on the plane, such as flight attendants, passengers, medical staff and immigration officials, have all been quarantined in their respective homes and are being monitored for signs of MERS.

The agency said that 435 people who came into ordinary contact with the MERS patient are currently being monitored. They have not been quarantined, but they have to report their health conditions every day to officials in charge of monitoring.

MERS is a viral respiratory disease with a fatality rate of 20-46 percent. It is caused by a novel coronavirus carried by camels and can be spread when someone is in close contact with a patient for a sustained period.

The first MERS case was recorded in Saudi Arabia, and it has since spread to other countries. As of June this year, the World Health Organization has reported 2,229 laboratory-confirmed cases.

South Korea was hit by an outbreak in 2015, resulting in 38 deaths and 186 people testing positive for MERS. (Yonhap)